1. Field of the Invention
This invention relates to data processing systems which employ a host computer or central processing unit and an external data source such as a disk drive or tape unit to provide data to the central processing unit. More particularly, this invention relates to data processing systems which include a peripheral controller for controlling the operation of the external data source, including transfer of data to the central processing unit.
2. Description of the Prior Art
The performance of computer systems has been improved by providing peripheral controllers to perform various standard functions in order to off-load input/ouput processing from the central processing unit ("CPU") to free it for performing more complex operations. Among the most complex controllers are disk controllers, which mate a CPU with a magnetic disk drive data storage unit.
Recent controller systems have included a buffer random access memory (RAM) connected to a controller in order to efficiently receive and store data from the CPU for subsequent transmission to the disk drive or vice versa. However, these prior art systems require that the CPU transmit data to and receive data from the RAM at a rate limited by the processing speed of the controller. The present invention eliminates that limitation, permitting the CPU to transmit data to and receive data from the RAM at the CPU's maximum data transfer rate.